The effect of hemodialysis and hemoperfusion on serum valproic acid concentration.

We report a patient with dialysis-induced encephalopathy who was taking divalproex sodium for a seizure disorder. Her serum valproic acid concentration appeared to be in the low therapeutic range at 54 mg/l yet she continued to have seizure activity. The elimination half-life and apparent clearance of valproic acid were the same for both a dialysis and nondialysis day, indicating that hemodialysis/hemoperfusion has little effect on the overall removal of valproic acid from the body.